In general, electronic circuits, for example integrated circuits (ICs), which operate in a clock-based manner, are used for a large number of functions. The clock frequency with which the electronic circuit is operated can for example define its power consumption, a higher clock frequency usually being accompanied by a higher power consumption. Consequently, an adaptation of the clock frequency can be used for example to optimize the energy consumption of an electronic circuit. A reduction of the clock frequency can also be used to protect the electronic circuit from overheating, for example in the form of so-called heat management.
In systems with a limited energy supply, for example in battery-operated or passively operated electronic circuits (for example in passive wireless communication circuits), it may be helpful to adapt the dynamic power consumption to the resources available (for example the available electrical voltage or electrical power). For example, contactlessly communicating chip cards, in the case of which the operating energy is fed in wirelessly (for example in the case of credit cards), obtain varying amounts of electrical power for operating them, depending on how far away they are from the reader. It may be helpful in this respect to interrupt the clock-based operation of the electronic circuit when the supply voltage for the electrical circuit to be operated falls below a predefined supply voltage. In this way it is possible for example to avoid faulty operation of the electronic circuit. When a sufficient supply voltage or electrical power is available again, for example above the predefined supply voltage, the clock-based operation of the electronic circuit can be continued. The interruption of clock-based operation of an electronic circuit may be referred to for example as a clock stop. For example, a clock signal may be deliberately suppressed.
By means of a voltage-controlled oscillator, it is possible to generate on the basis of an input voltage a clock frequency assigned to the input voltage. This can for example make it possible when there is a falling supply voltage (as the input voltage of the voltage-controlled oscillator) of a circuit also at the same time to lower the clock frequency, and consequently the energy consumption. This alone however does not allow for the requirement that, as from a minimum supply voltage, a clock is no longer to be processed.